A suicide bomber threw a hand grenade and blew himself up at a police station in Turkey’s biggest city on Tuesday, killing one police officer and wounding seven other people, authorities said.

Ambulances raced to the scene of the blast in an Istanbul suburb after the attack. Forensic investigators then moved in, combing the area in front of the building for evidence.

The city’s police chief, Huseyin Capkin said the assailant was a 25 year old man.

There was no immediate claim of responsibility. Fighting between Turkish forces and Kurdish rebels who seek self-rule has surged in recent months. The military announced on Monday that it had conducted air strikes over the past week in northern Iraq, where Kurdish rebels have bases. Some 25 guerrillas were killed in the operation, according to the military.

Authorities blamed the rebel Kurdistan Workers’ Party for a bomb last month that killed nine people near a police station in a city close to the Syrian border. Rebels denied involvement, though they have escalated attacks in what some analysts believe is an attempt to capitalize on regional uncertainty surrounding the civil war in Syria.